If you were over by the East End yesterday afternoon, you might have heard a strange yelping sound that didn't come from Frick Park's off-leash area. A new survey by upstart pollsters Keystone Analytics shows Jack Wagner beating Bill Peduto by a 38-30 margin. It's the first poll to show Peduto trailing anyone but Mayor Luke Ravenstahl, the incumbent.

There are a few reasons to take this poll with a grain of salt. First, as I pointed out when Keystone showed Peduto leading, this is a new outfit that has never done political polling before. Their reliability remains unproven. Second, the same poll shows a margin of error of nearly 5 percent and 23 percent of voters undecided. With TV ads yet to be unveiled, that leaves a lot of room for all the candidates to maneuver.

You can also argue that the sample wasn't representative. Peduto's campaign has pointed out that the sample included few young voters: Only 7 percent were in the 18-to-34 age bracket -- and younger voters are much more likely to back Peduto. Of course, as we saw in 2009, in municipal primaries the city's electorate skews way, WAY old ... but even then, the percentage of 18-to-34-year-old voters was in the double digits. And in that election, there was little expectation that Luke Ravenstahl would lose against two ill-funded challengers. A more competitive race might draw more younger voters out.

And yet ... the most notable polling dynamic here may not be the fact that Wagner moved up, but that Peduto barely moved at all.

As the Pedutoistas at Keystone Politics point out, Wagner was always going to gain ground, as news of his candidacy sunk in and as other contenders dropped out and backed him. But Peduto's 30 percent remains unchanged since thelast Keystone Analytics poll, taken a month ago. The number of undecided voters, meanwhile, has also remained relatively stable -- 22 percent in early March versus 23 percent today. If the new numbers are right, it suggests Wagner has been consolidating support from would-be Ravenstahl voters. And that Peduto hasn't yet made the headway with undecideds he'll need to overcome that momentum.

Political observers I've spoken with say this is a critical -- and potentially worrisome -- moment for Peduto. By their lights, Peduto has always had a rock-solid base that amounts to somewhere between one-quarter and one-third of the electorate. And for a little while, it looked like that's all he might need. When the field was cluttered up with a half-dozen candidates, winning with a third of the vote (or less) was mathematically quite possible. The fact that Peduto's support was so consistent -- as the whole rest of the field changed around him -- looked like a source of strength. But that's going to change as this solidifies into a two-person race. (The Keystone Analytics poll shows that AJ Richardson and state Rep. Jake Wheatley with 5 percent of the vote between them.)

Still, there's plenty of time between now and Election Day, and a lot of those undecided voters probably haven't started paying attention. Peduto has been cobbling together a coalition that includes labor unions, South Hills pols and progressive-minded groups like gun-control advocacy group CeasefirePA. In recent days he's unveiled endorsements from state Rep. Ed Gainey, a longtime ally, City Councilor Patrick Dowd, a onetime foe.

What's more, even if voters haven't picked their messenger yet, they do seem receptive to Peduto's message.

One overlooked Keystone poll finding was the answer to the question "which issue is most important to you?" Jobs and economic development came in first, of course, followed by "investing in schools." But coming in third was "investigating government corruption" -- and all three top-tier answers were within a couple percentage points of each other. I don't want to overstate that result (for one thing, public safety and crime concerns weren't among the list of choices.) But when Pittsburghers are more concerned about public integrity than potholes -- only 9 percent of voters cited road conditions as their top issue -- there's clearly some unease out there for a politician to capitalize on.

The race may well hinge on whether Peduto or Wagner is best equipped to do so.